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47 Cards in this Set
- Front
- Back
Aliphatic AAs
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-Glycine (Gly)
-Alanine (Ala) -Valine (Val) -unreactive -limited flexibility, molecular stability -apolar face of alpha helix and b sheet and in core globular proteins -Leucine (Leu) -Isoleucine (Iso) |
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Aromatic AAs
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-Phenylalanine (Phe)
-Tyrosine (Tyr) -OH group makes it very reactive -Tryptophan (Trp) -used to quantify proteins because it can adsorb @ 280nm |
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Proline
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-breaks alpha helix
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Sulfur Containing AAs
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-Cystine (Cys)
-2 cysteine sulfides are oxidized to form Cystine -Methionine (Met) -Cysteine and disulfide bonds, impact thermostablity and folding confirmations -at neutral and alk pH rapid exchange of thiols |
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Polar AAs
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-Serine (Ser)
-Threonine (Thr) -amide groups of asn and gln are labile at extreme pH |
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Basic AAs
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-Histidine (His)
-Lysine (Lys) -Arginine (Arg) -charged in foods: lys and arg -salt bridge interactions |
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Acidic AAs
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-Aspartate (Asp)
-Glutamate (Glu) -Aspargine (Asn) -chelate metal ions; calcium binding -H donors -salt bridge interactions -Glutamine (Gln) |
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pH < pKa
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AA is (+)
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pH > pKa
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AA is (-)
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Primary Structure
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-Ala-Glu-Val-Thr-
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Secondary Structure
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-Alpha helix
-Beta sheet |
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Tertiary Structure
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Domains
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Quaternary Structure
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-comprised of subunits
-hydrophobic patches lead to quaternary structure -Myosin (functional protein in muscle) has 6 subunits |
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Disulfide
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-covalent bond b/w cys residues
-restricts number of confirmations that proteins can assume |
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Bond Energies
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-C-C
-S-S -H bond -Salt ionic -Hydrophobic -Van der Waals |
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Urea
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-causes proteins to unfold and break sulfide bridges
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Forces that stabilize protein structure
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- H bonds
-Electrostatic interactions -depends on charge - charges is on surface usually but inside structure its stabilizing -Hydrophobic interactions -No net attraction -thermodynamically driven; H20 -Dipole-Dipole -Disulfide linkage |
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Hydrophobicity and proteins
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-not true bonds
-food proteins tend to hbp -can lead to quarternary structure when there are hydrophobic residues on surface -more hpb, more tend to aggregate -can serve as good gelling, water holding and fat holding agents |
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Functional proteins in eggs
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-ovalbumin
-responsible for foaming |
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Functional proteins in meat
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-Myosin
-highly functionally -responsible for quality of meat |
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Protein solubility important in...
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-beverages
-protein concentrates |
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Protein water holding capacity important in....
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-meats
-cheese -yogurt -surimi |
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Protein gelatin is important...
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-comminuted meat
-custards -scrambled eggs -yogurt -tofu |
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Protein emulsification is important in
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-mayo
-salad dressing -gravies -ice cream |
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Protein foaming is important in
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-whipped toppings
-meringues marshmellows |
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Salting in
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-increasing protein solubility by addition of salt
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Salting out
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-precipitating proteins
-decreasing of protein solubility -increase NaCl; increase net solubility at PI |
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PI
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-no net charge on protein
-max protein interactions -less likely to be soluble at PI |
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pH = pKa
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aa has no net charge
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pH < PI
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-net charge on protein is (+)
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pH > PI
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-domains of
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Shear Stress
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-force put on an object at an angle
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Shear Strain
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-how a product deforms
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NaCl
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-increases protein solubility
-used as an control |
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KSCN
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-enhances protein-solvent interactions
-get looser gel |
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(NH4)2SO4
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-enhances protein-protein interactions
-get more solid gel |
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Myosin quarternary structure
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-2 heavy chains
-forms alpha helical tail -4 light chains in globular head -ATP activity is centered -cause traction and relaxation (movement) |
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Myofibril
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-G-actin (globular) polymerizes to form F-actin (fibrous)
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Power stroke of muscle and motility
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1. energized myosin on signal from regulatory protein; binds ADP,Pi
2. myosin makes contact with G-actin 3. confirmations change in myosin moves actin 4. release of bound ADP, Pi; cleavage of ATP changes myosin t original position |
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Structural hierarchy of muscle
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-fiber bundles: form muscle structure
-myofilament -contain myosin and actin (salt soluble) -contains structural and functional proteins -Sarcoplasma proteins -catalytic proteins -surrounds fiber bundles -myosin inches down actin chain w/energy Structure fiber bundles -> myofibrils ->myofilament ->sarcoplasma |
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TEM of muscle structure
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-regular repeating highly ordered structure
-myofibril, Z-line, A band, I band Sacromere |
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Thick and thin filaments
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-lil hairs where catalytic activity takes place (contractions)
-arrangement of filaments in skeletal muscle. -thick is myosin thin is actin |
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Water Soluble Proteins (WSP)
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-not functional for whipping etc.
-not useful in food science -contains sacroplasmic enzymes |
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Salt Soluble Proteins (SSP)
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-want to maintain quality of these proteins
-functional proteins |
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Fresh muscle, rigor and quality
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-@ slaughter theres a depletion of energy stores
-increase in lactic acid -decrease in glycogen -anaerobic stiffening -myosin binds to actin and won't unbind until relaxation (post rigor) |
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Gelling
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Association of dispersed polymer chains in solution to form a 3d continuous network, immobilizes liquid in interstatial structures, resists flow
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Phosphates
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-disrupt sarcomere by breaking down ordered structuure by making it hold H2O better.
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